JP3067124B2 - Injection molding method for molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection flow press (hereinafter referred to as "injection") of a material having a relatively low melting point, such as aluminum and aluminum alloy, or magnesium and magnesium alloy, in a molten state, semi-solid state or solidified state. The present invention relates to an injection molding method of a molding device such as a die casting machine or a squeeze cast machine for obtaining a product having a desired shape. The present invention relates to an injection molding method of a molding apparatus for obtaining a molded product.

[0002]

2. Description of the Related Art A die casting machine is, for example, a method in which an aluminum alloy or a magnesium alloy is heated in a melting furnace to be in a molten state (hereinafter referred to as a molten metal), poured into a cylinder shown in FIG. By repeatedly injecting a molten metal into the mold cavity 3 and mechanically opening the mold from the dividing surface after cooling and solidifying to take out the product,
This device can mass-produce aluminum alloy products and magnesium alloy products. The injection piston 6A and the injection cylinder 6 (5
The horizontal direction is called horizontal casting, and the vertical direction is called vertical casting. The type in which the split surface of the mold opens horizontally is called horizontal clamping, and the type in which it opens vertically is called vertical clamping. These combinations are referred to as a horizontal clamping vertical casting type or the like, but the most common types are a horizontal clamping horizontal casting type (hereinafter referred to as a horizontal type) and a vertical clamping vertical casting type (hereinafter referred to as a vertical type).

In the case of the horizontal type, as shown in FIG. 13, there is a gas reservoir in the upper half of the sleeve 5 due to its structure, and when the injection piston 6A moves at a high speed, the gas above the sleeve 5 is entrained into the molded product. The sealing results in a reduction in the mechanical strength of the product. Further, when heated, blisters (local swelling) are generated, so that heat treatment cannot be performed.
In addition, when the gas in the mold cannot escape in time, entrainment of the gas is inevitable. Further, when the molten metal is jetted at a high speed along a path (hereinafter referred to as a gate 7) from the sleeve 5 to the mold cavity 3, the gas in the mold is easily entrained. Therefore, the speed of the injection piston 6A is normally low when the tip of the molten metal passes through the sleeve 5 and the gate 7, and then increased in accordance with the shape of the mold. In addition, since injection must be completed before solidification, low-speed injection is also limited.

On the other hand, in the case of the vertical type, as shown in FIG. 14, gas can easily escape upward when hot water is supplied, so that entrainment of the gas in the sleeve 5 can be avoided. As a result, a high quality casting without gas entrainment in the gate 7 and the mold can be obtained. Therefore, the horizontal type is used to produce high-quality products by injecting at high speed, and the vertical type is used to produce high-quality products by injecting at low speed and sufficiently releasing gas. ing.

In general, the former method is called a die casting method (DC
Method), and the latter is called the squeeze cast method (SC method). In the die casting method and the squeeze casting method, the material is in a molten state, whereas in the thixocasting method, the material is in a semi-solid block shape. in recent years,
Some horizontal-type squeeze machines also perform low-speed injection. The biggest technical problem of these low-speed injection methods is how to determine the injection speed in order to prevent gas entrainment in the sleeve, gate and mold.

[0006] From the above, conventionally, in the die-casting method of horizontal clamping horizontal casting, in the initial stage of normal injection filling, low-speed injection with a gate speed of 0.5 to 2 m / s is performed.
High-speed injection with a gate speed of 30 to 60 m / s is performed after the tip of the molten metal passes through the gate. On the other hand, in the squeeze method, the module (specific surface area per unit volume of the molten metal) in the sleeve is small, the temperature drop of the molten metal during injection filling is smaller than that in the die casting method, and the safety against solidification of the molten metal is high. Therefore, a low-speed injection with a gate speed of 0.5 to 2 m / s is performed from the start of injection filling to the completion of injection filling, and a high quality molded product is obtained.

[0007]

However, when a molded product is a thin product having a thickness of, for example, about 2 mm to 4 mm, or when a molded product has a thin portion of about 2 mm, a die casting method or a squeezing method is used. In the above-mentioned injection method, sufficient running of the molten metal in the thin portion in the mold cavity cannot be expected, so that a molded product having high strength without casting defects cannot be obtained. In the present invention, a molded article having such a thin portion is produced without casting defects.
Further, an object of the present invention is to provide an injection molding method having high strength.

[0008]

In order to solve the above-mentioned problems, in the present invention, a metal molding material having fluidity by heating or pressurizing means flows into a substantially closed mold cavity. This is an injection molding method for a molding machine that repeatedly produces a molded product whose main part is formed with a thin part by press-fitting. Observation of flow behavior in the cavity by water flow test using a thin transparent plastic model in advance and wall thickness Gate speed for filling the laminar flow in the cavity in order to obtain a sound molded product without gas entrapment
The gate speed is 0.1 to 0.5 m / s from the start of injection filling to the allowable limit filling amount corresponding to the thickness of the thin portion. Injection filling is performed, and after reaching the permissible limit filling amount, an ultra-high speed injection filling with a gate speed of 60 to 360 m / s is performed. Further, in the second invention, a metal molding material having fluidity by heating or pressurizing means is flow-pressed into a substantially closed mold cavity to repeatedly produce a molded article whose main part is formed of a thin portion. a injection molding method of molding apparatus that performs verification by molding test of several flat plate-cast specimens of different observation and the thickness of the cavity flow behavior due to water flow test using a previously thin transparent plastic model , gate for the cavity inner flow filling in order to obtain a sound molded product with no gas entrainment
And the correlation between the molding speed and the allowable limit filling amount and the correlation between the molded product thickness and the limit filling amount for preventing run-out failure in the mold cavity. until a permissible limit loadings gate velocity implement ultra slow injection filling of 0.1-0.5 M / s, the gate from reaching the tolerable charge until reaching the misruns limit loading The speed is low-speed injection filling of 0.5 to 2 m / s or high-speed injection filling of 2 to 60 m / s. Ultra high-speed injection filling was decided.

[0009]

In the present invention, a metal molding material is subjected to a molding test or a molten metal flow test in a cavity by using various types of flat cast test pieces having different thicknesses under the same molding conditions as during operation. When the molten metal is injected and filled, the tip surface of the molten metal proceeds uniformly, that is, the allowable limit filling amount corresponding to the pre-filling amount required for the so-called laminar flow filling to proceed is determined for each thickness. During operation, the gate speed of the injection filling is 0.1 to 0.5 m / s so that turbulence does not occur until the wall thickness reaches the allowable limit filling amount corresponding to the minimum product thickness.
Ultra low speed injection filling. Since these pre-filled layers are formed in the mold cavity, laminar flow filling is performed without causing turbulent flow at any high injection speed until the filling is completed thereafter. Since there is no gas entrainment on the surface, the gate speed is set to 60 to 360 m / h to complete filling in as short a time as possible and to prevent poor running.
s ultra-high-speed injection filling to obtain a dense molded product without gas entrainment. In the second invention, together with the allowable limit filling amount for laminar flow filling, the limit filling amount for preventing run-out failure in the mold cavity for each wall thickness is grasped. On the orthogonal coordinate plane of the filling amount in the cavity, the ultra-low-speed filling region, the composite filling region, and the ultra-high-speed filling region, which are divided into regions separated by the laminar flow allowable limit line and the runoff prevention prevention limit line, respectively, are determined. In the ultra-low speed region from the start of injection filling to the allowable limit filling amount in the mold cavity corresponding to the thickness of the molded product thin portion based on the divided region, the gate speed is 0.1 to
Ultra-low speed injection filling of 0.5 m / s is performed, and in the composite filling region, low speed injection filling of 0.5 to 2 m / s, or 2 to 60 m / s.
m / s high-speed injection filling is performed, and in the ultra-high-speed filling region exceeding the run-out failure prevention limit line, 60-360 m / s ultra-high-speed injection filling is performed, so that there is no gas entrapment and the run-out defect is low. Not get excellent molded products.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 11 relate to an embodiment of the present invention, FIG. 1 is a characteristic curve diagram showing a correlation between a gate speed and a permissible limit filling amount for laminar flow filling in a cavity, and FIG. 2 is a product minimum wall thickness and cavity filling. Fig. 3 is an explanatory diagram showing the results of a water flow model experiment using a transparent plastic model, Fig. 4 is a dimensional shape diagram of a flat cast test piece, and Fig. 5 is a case where a preliminary filling layer is provided. FIG. 6 is an explanatory diagram showing the results of a water flow model experiment using a transparent plastic model, FIG. 6 is a comparative explanatory diagram of the water flow behavior with and without a pre-packed bed, and FIG. 7 describes the flow behavior when a pre-packed bed is provided. FIG. 8 is a comparison diagram of the metal structures of the present invention and the conventional example, FIG. 9 is a graph showing a tensile strength test result of a molded article according to the present invention, FIG. 10 is a graph showing an elongation test result of a molded article according to the present invention, Figure 1 is a graph showing the fatigue test results.

In the present invention, as a factor having an adverse effect on the quality of the molded product, casting defects occur due to entrainment of gas at the time of injection filling into the mold cavity, and molten metal caused by solidification of the molten metal occurring during the injection filling time. In order to solve the problem of casting defects caused by poor running of the molten metal, through a visualization experiment of the flow behavior in the cavity based on a transparent plastic model, the cause of gas entrainment during injection filling is the undulation at the tip of the molten metal Focusing on the phenomenon caused by the phenomenon, the flow of molten metal during injection filling is changed from the turbulent state that causes such ripples to pursue the limit condition that maintains such laminar flow without ripples, the gas at the tip of the molten metal We thought that entrapment could be prevented. The test results of the flow visualization model described later and the verification of the quality of the molded product obtained as a result of the molding test of the flat cast test piece based on the test results show that the forming conditions are the critical conditions for laminar flow that can prevent gas entrapment. Along with the product thickness and the gate speed at the time of injection filling, the filling amount of the pre-filled layer in which the molten metal was previously injected into the mold cavity at the start of injection filling (hereinafter, defined as the percentage of the pre-filling volume in the total filling volume in the cavity) , In other words, also referred to as the filling rate). The details will be described below.

To implement the flow visualization model, a parallel cast test piece (width 100 mm, length 200 m) shown in FIG.
m, a transparent plastic model (made of acrylic resin) having the same spatial shape as the plate thickness tmm (arbitrary), as shown in FIG.
(thickness mm × 20 mm width × 3 pieces), and water colored with black ink was allowed to flow at various speeds upward from a lower gate opening having a width of 40 mm. The thickness of the cavity used in the transparent plastic model was 3, 10 and 20 mm. FIG. 3 shows a transparent plastic model having a thickness of 10 mm and a gate speed v of 1.57 m / s (corresponding to FIG. 3A) and 0.31 m / s (corresponding to FIG. 3B). This is a reproduction of a situation in which water is flown from outside without being formed in advance, which is taken by a high-speed camera. According to the results of FIG. 3, when there is no pre-packed layer, the flow becomes turbulent when the gate speed v is 1.57 m / s, but is extremely good when the gate speed v is very low at 0.31 m / s. Laminar flow. The viscosity of water at room temperature is rheologically equivalent to that of a molten metal such as an aluminum alloy or a magne alloy at about 700 ° C. According to the above-mentioned results, the conventional water has a viscosity of 0.5 to 2 m / s (up to 1 m / s for some people). In the region, it is assumed that the molten metal flows in the cavity by laminar flow, but it has been found that these conventional techniques are obviously reversed. On the other hand, FIG. 5 shows the pre-filled layers in which the filling amount F = 2.5% (corresponding to FIG. 5 (a)) and 5% (corresponding to FIG. 5 (b)) (cavity height 5 mm, 10 mm respectively) in the cavity. FIG. 5 shows a flow visualization model experiment in which water was flowed at a gate speed v = 1.57 m / s after injecting water in advance, and as is clear from FIG. Is 2.5%, the flow is disturbed and bubbles are formed inside the fluid,
When the filling amount F is 5%, the rising of the liquid level at the tip is observed, but no bubbles are formed inside the fluid. FIG. 6 shows a high-speed injection of a gate speed v = 15.7 m / s (corresponding to FIG. 6A) after forming a pre-filled layer by low-speed filling to a height of 50 mm (filling amount 25%). In the case of a high-speed injection at a gate speed v = 15.7 m / s without any pre-filled layer (corresponding to FIG. 6B), gas entrainment was generated in a turbulent state. No such signs are seen at all, and it can be seen that the liquid level at the tip flows in an ideal laminar state.

As a result of repeating various visualization model experiments on such a flow behavior, a characteristic curve showing a correlation between a gate speed for laminar flow filling in a cavity and an allowable limit filling amount as shown in FIG. 1 was obtained. The characteristic curve X1 in the figure is a laminar flow filling permissible limit line indicating the limit of the required filling amount (preliminary filling amount) that enables laminar flow filling, and increases as the gate speed v increases. about 25 seconds or more
%. Point A in FIG. 1 indicates a gate speed v = 0.3.
At an extremely low speed of m / s, a point at which laminar flow occurs even without a pre-packed bed is indicated, such as point B1 (gate speed 1.6 m / s, no pre-fill amount) or point B2 (gate speed 1.6 m / s). , The pre-filling amount F = 2.5%), the laminar flow does not occur, and FIG.
As described above with reference to FIG. 5A and FIG. 5A, the flow becomes turbulent and gas entrainment occurs. On the other hand, the pre-filled layer was filled with F = 5
% (Corresponding to FIG. 5 (b)), laminar flow is formed, and desirable injection filling without gas entrainment is possible.

Further, in the present invention, in addition to the flow visualization model experiment, in order to eliminate casting defects caused by solidification of the molten metal occurring during the injection filling time of the molten metal, the thickness t of the thin plate model and the solidification time T are determined. Estimated by the following equation, which is obtained as a correlation: solidification time T (sec) = 0.033 t ² , the horizontal axis represents the thickness (minimum product thickness) t, and the vertical axis represents the orthogonal filling plane with the cavity filling amount F. As a condition for forming a laminar flow and preventing solidification from progressing within the injection filling time, the correlation between the minimum wall thickness of the product and the cavity filling amount divided in the ultra low speed filling region, the composite filling region, and the ultra high speed filling region Was formed as shown in FIG. According to FIG. 2, the laminar flow allowable limit line Y1 is the filling rate F
= 25%, and the limit line Y2 for preventing run-off is a curved curve that is convex upward. In the present invention, the injection filling speed into the cavity is made extremely low (0.1 to 0.5 m /
s), low speed (0.5-2 m / s), high speed (2-60 m / s)
s) and ultra high speed (60 to 360 m / s), the injection filling speed defined in the prior art is either low speed injection filling or high speed injection filling. The significance of the three filling speed regions shown in FIG. 2 is as follows. In the ultra low speed filling region, since the cavity filling amount F is 25% or less, the speed is set as low as possible so as not to induce gas entrainment until a pre-filled layer is formed. This is a region where the cavity is gently filled so as to form a laminar flow at an extremely low speed of 0.1 to 0.5 m / s. Laminar flow allowable limit line Y for cavity filling F = 25%
The injection filling speed (gate speed) is 0.5 m / g because the composite filling region between the first filling limit line Y2 and the run-out failure prevention limit line Y2 is after the preliminary filling layer having the cavity filling amount F exceeding 25% is formed. The laminar flow is maintained at the tip surface even if it exceeds s,
This is an area where filling may be performed at a low speed of 0.5 to 2 m / s or at a high speed of 2 to 60 m / s. The region above the run-out failure limit line Y2 is an ultra-high-speed filling region. Unless injection filling at an ultra-high speed of 60 m / s or more is performed, solidification of the molten metal proceeds during injection filling, resulting in poor running. It is necessary to complete injection filling quickly. The area where the minimum product thickness t is 1.6 mm or less is an unknown area where no experiment has been performed, and is a subject to be solved in the future.

From the above, the minimum product thickness t is 1.6.
When molding a molded product in the range of 10 mm to 10 mm, injection molding is performed at a very low speed to prevent turbulent flow until the pre-filled layer is formed after the start of the injection molding. The injection is performed at a low or high speed until the cavity filling amount reaches a different limit line for preventing run-out failure, and thereafter, the ultra-high-speed injection is performed until the filling is completed. The above corresponds to the second invention. On the other hand, in a molded product having a thin part having a thickness t of about 1.6 mm as a main part, injection filling is performed at an extremely low speed until a pre-filled layer is formed, and thereafter ultra-high speed injection is performed until the filling is completed. I do. This corresponds to the first invention.

In order to demonstrate the above technical knowledge,
A molding test using a thin plate cast specimen was performed. The adopted thickness t is 1.6mm, 2.5mm, 4mm, 5m
m and 6.3 mm, and has a rectangular parallelepiped shape having a width of 100 mm and a height of 200 mm, as shown in FIG. FIG. 8 is a micrograph (magnification: 200) of a micrograph showing the metallographic structure of the flat cast test piece according to the present invention. When the conventional structure is observed macroscopically, gas defects (pinholes, blowholes) due to air entrapment. However, in the present invention, they are not recognized and a dense metal structure is formed. Further, when observed microscopically, the eutectic structure exhibits acicular Si in the conventional method, whereas the eutectic structure is improved in the form of granular or fine fibrous Si in the method of the present invention. Recognize. In addition, as shown in FIGS. 9 and 10, the results of the tensile test and the elongation test were far superior to those of the conventional example. Further, as shown in FIG. 11, the results of the fatigue test were better than those of the conventional example. The present invention is most suitable for molding, for example, disk wheels and small parts of automobiles whose main parts are thin, household appliances (hot plates), and panel-like molded products formed entirely of uniform thin parts.

[0017]

As described above, according to the injection molding method of the molding apparatus of the present invention, when a molded product having a thin portion in its main part is injection-molded, there is no entrainment of gas and a good height of the molten metal can be obtained. It is possible to obtain a dense and excellent molded product having high strength.

[Brief description of the drawings]

FIG. 1 is a characteristic curve diagram showing a correlation between a gate speed and an allowable limit filling amount for laminar flow filling in a cavity according to an embodiment of the present invention.

FIG. 2 is an injection filling speed division diagram in a correlation between a product minimum thickness and a cavity filling amount according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a water flow model experiment result using a transparent plastic model according to an example of the present invention.

FIG. 4 is a dimensional shape diagram of a flat cast test piece according to an example of the present invention.

FIG. 5 is an explanatory diagram showing the results of a water flow model experiment using a transparent plastic model when a pre-filled layer according to an embodiment of the present invention is provided.

FIG. 6 is a comparative explanatory diagram regarding a water flow behavior with and without a pre-packed bed according to an example of the present invention.

FIG. 7 is an explanatory diagram illustrating a flow behavior state when a pre-packed bed according to an embodiment of the present invention is provided.

FIG. 8 is a comparison diagram (schematic diagram) of the metal structures of the present invention example and the conventional example.
It is.

FIG. 9 is a graph showing a tensile strength test result according to an example of the present invention.

FIG. 10 is a graph showing an elongation test result according to the example of the present invention.

FIG. 11 is a graph showing a fatigue test result according to the example of the present invention.

FIG. 12 is an overall configuration diagram of a conventional molding apparatus.

FIG. 13 is a schematic vertical cross-sectional view illustrating a state of injection filling in a conventional molding apparatus.

FIG. 14 is a schematic longitudinal sectional view for explaining the injection filling state of a conventional horizontal clamping vertical casting type molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding apparatus 2 Fixed mold 3 Cavity 4 Movable mold 5 Sleeve 6 Injection cylinder 6A Piston 7 Gate v Gate speed in mold cavity (gate speed) F Cavity filling amount (cavity filling rate) X1 Laminar flow filling limit line Y1 Permissible limit line for laminar flow Y2 Limit line for preventing run-out failure t Minimum product thickness (product thickness) G Gas M Molten metal

Claims (2)

(57) [Claims] 1. A molding apparatus for flowing a metal molding material having fluidity by heating or pressurizing means into a substantially closed mold cavity, and repeatedly producing a molded product having a main portion formed of a thin portion. Injection molding method, using a thin transparent plastic model to observe the flow behavior in the cavity by a water flow test and verify by a molding test of several types of flat cast test pieces with different wall thickness, calibration in order to obtain a no sound moldings
The correlation between the gate speed for filling the inner laminar flow and the allowable limit filling amount is grasped, and the gate speed is set to 0.1 from the start of injection filling to the allowable limit filling amount corresponding to the thickness of the thin portion. ~ 0.5m / s ultra low speed injection filling
After reaching the allowable limit, the gate speed is reduced to 60-36.
An injection molding method for a molding apparatus that performs ultrahigh-speed injection filling at 0 m / s. 2. A molding apparatus for flowing a metal molding material having fluidity by heating or pressurizing means into a substantially closed mold cavity, and repeatedly producing a molded product whose main part is formed by a thin part. Injection molding method, using a thin transparent plastic model to observe the flow behavior in the cavity by a water flow test and verify by a molding test of several types of flat cast test pieces with different wall thickness, calibration in order to obtain a no sound moldings
The correlation between the gate speed and the allowable limit filling amount for filling the inner laminar flow and the correlation between the molded product wall thickness and the limit filling amount for preventing run-out failure in the mold cavity are grasped. Mold cavity tolerance corresponding to
Gate speed is 0.1-0.5m until the boundary filling amount is reached
/ S low-speed injection filling at a gate speed of 0.5 to 2 m / s from the time of reaching the permissible limit filling amount to the time of reaching the limit filling amount for preventing run-off failure. Alternatively, an injection molding method for a molding apparatus that performs high-speed injection filling at 2 to 60 m / s.